2-perchlorocrotonylamino-5-trifluoromethyl-1,3,4-thiadiazole

ABSTRACT

2-(N-acyl)-amino-1,3,4-thiadiazoles, i.e. 2-(N-(optionally alkyl)-N-(alkanoyl, chloroalkanoyl, fluoroalkanoyl, alkenoyl, chloroalkenoyl, alkoxycarbonyl, alkoxyalkoxycarbonyl, alkenyloxycarbonyl, alkynyloxycarbonyl, and phenoxycarbonyl)amino)-5-trifluoromethyl-1,3,4-thiadiazoles, which possess herbicidal properties, and which may be produced by conventional methods.

United States Patent Rucker et al.

14 1 Apr. 17, 1973 Filed:

Z-PERCHLOROCROTONYLAMINO-S- TRIFLUOROMETHYL-1,3,4- THIADIAZOLEInventors: Dietrich Rucker, Wuppertal-Elberfeld; Ludwig Eue, Cologne-Stammheim; Helmuth Hack, Cologne-Buchheim, all of Germany FarbenfabrikenBayer Aktiengesellschaft, Leverkusen, Germany July 16, 1969 Appl. N0.:842,369

Assignee:

Foreign Application Priority Data Aug. 1,1963 Germany ..P 17 95 037.7

ms. C1. ..260/306.8 1), 71/90 Int. Cl. ..C07d 91/62 Field of Search..260/ 306.8 D

. [56] References Cited UNITED STATES PATENTS 3,564,002 2/197I Remers etal "260/3068 OTHER PUBLICATIONS Lalezari et 211., J. I-IeterocyclicCh1em., 3(3), 336-337 (1966).

Primary ExaminerAIex Mazel Assistant Examiner-R. J. GallagherAttorney-BUrgess, Dinklage & Sprung [5 7 ABSTRACT 1 Claim, No Drawings'Z-PERCHLOROCROTONYLAMINO-S- TRlFLUOROMETHYL-l ,3 ,4-THIADIAZOLE Thepresent invention relates to and has for its objects the provision forparticular new 2-(N-acyl)- amino-l,3,4-thiadiazoles, i.e.2-[N-(optionally alkyl)- N-(alkanoyl, chloroalkanoyl, fluoroalkanoyl,alkenoyl, chloroalkenoyl, alkoxycarbonyl, alkoxyalkoxycarbonyl,alkenyloxycarbonyl, alkynyloxycarbonyl, andphenoxycarbonyl)-amino]-5-trifluoromethyl-1,3,4- thiadiazoles, whichposses valuable, especially selective, herbicidal properties, activecompositions in the form of mixtures of such compounds with solid andliquid dispersible carrier vehicles, and methods for producing suchcompounds and for using such compounds in a new way, especially forcombating weeds, undesired plants, and the like, with other and furtherobjects becoming apparent from a study of the within specification andaccompanying examples.

It is known that carboxylic acid amides such as propionic acid3,4-dichloroanilide (A) [German Published Patent Specification No.1,039,779] and carbamates such asisopropyl-N-(3-chloro-phenyl)-carbamate (B) [U.S. Pat.No. 2,734,911] canbe used as herbicides.

It has now been found, in accordance with the present invention, thatthe particular new 2-(N-acyl)- amino-1,3,4-thiadiazoles of the formula:

R is trifluoromethyl,

R is hydrogen or alkyl of one to four carbon atoms, and R" is alkyl ofone to five carbon atoms, chloro-substituted alkyl of one to threecarbon atoms, fluoro-substituted alkyl of one to three carbon atoms,alkenyl of two to fourcarbon atoms,

, chloro-substituted alkenyl of two to four carbon atoms, alkoxy of oneto four carbon atoms, alkoxyalkoxy having one-to two carbon atoms ineach corresponding alkoxy moietyIalkenyloxy of two to four carbon atoms,alkynyloxy of three carbon atoms, or phenoxy,

exhibit strong herbicidal, in particular selective herbicidal,properties.

It has been furthermore found, in accordance with the present invention,that a process for the production of the particular new compounds offormula (I) above may be provided, which comprises a. reacting aZ-amino-l ,3,4-thiadiazole of the formula:

in which R and R are the same as defined above, in the presence of anacid-binding agent, with a carboxylic acid halide of the formula:

R"-CO-Hal III in which i R is the same as defined above, and

Ha] is halogen such as chloro, bromo, fluoro or iodo, especially chloro:or t b. reacting a Z-amino-l,3,4-thiadiazole of the formula (II), withan acid anhydride of the formula:

in which R" is the same as defined above.

his decidedly surprising that the Z-(N-acyD-aminol,3,4-thiadiazolesaccording to the present invention exhibit a stronger herbicidalactivity and, in particular, a better selective-herbicidal activity thanthe previously known compounds such as (A) and (B) noted above. Theinstant compounds therefore represent avaluable enrichment of the art.

If Z-amino-S-trifluoromethyl-l,3,4-thi,adiazole and dichloroacetylchloride are used as starting materials, the reaction course accordingto process variant [a] can be represented by the following reactionscheme:

NWN

(Ila) (Illa) N-N If propionic anhydride is used for the reaction withthe same thiadiazole, thereaction course of the process variant [b] can.be represented by the following reaction scheme:

Advantageously, in accordance with the present invention, in the variousformulae herein:

R represents trifluoromethyl; R represents hydrogen; or straight andbranched chin lower alkyl hydrocarbon of one to four carbon atoms suchas methyl, ethyl, nand iso-propyl, n-, iso-, sec.- and tert.-butyl, and

the like, especially C, or C alkyl, and morefluoro-substituted loweralkyl of one to three carbon atoms such as mono, di and tri chloro--methyl, ethyl, nand isopropyl, and the like, especially mono, di andtri fluoro-C alkyl, and more especially trifluoromethyl;

straight and branched chain lower alkenyl hydrocarbon of two to fourcarbon atoms such as vinyl, a-, B and 'yallyl (i.e. prop-2-enyl,l-methyl-vinyl and prop-l-enyl), but-1,2 and 3-enyl, l-methyl-prop-l and2-enyl, and 2-methyl-prop-l and 2-enyl, and the like, especially Calkenyl, and more especially l-methyl-vinyl; chloro-substituted loweralkenyl of two to four carbon atoms such as mono to penta chloro-vinyl,a-, B, and y-allyl, but-1,2, and 3-enyl, l-methyl-propl and2-enyl, and 2-methyl-prop-l and 2-enyl, and the like, especiallychloro-substituted C alkenyl, more especially pentachloro-C alkenyl, andparticularly I,2,3,3,3-pentachloro-prop-l-enyl; straight and branchedchain lower alkoxy of one to four carbon atoms such as methoxy, ethoxy,nand iso-propoxy, n-, iso-, sec.- and tert.-butoxy, and the like,especially C or C, alkoxy; lower alkoxy-substituted lower alkoxy having1-2 carbon atoms in each corresponding alkoxy moiety such as methoxy andethoxy substituted methoxy and ethoxy, and the like, i.e. C alkoxy- Calkoxy, especially fl-methoxy-ethoxy; straight and branched chain loweralkenyloxy of two to four carbon atoms such as vinyloxy, a-, ,B- and 7-allyloxy (i.e. prop-2-enyloxy, l-methyl-vinyloxy and prop-l-enyloxy),but-1,2 and 3-enyloxy, 1- methyl-propl and 2-enyloxy, and 2-methyl-propland 2-enyloxy, and the like, especially C alkenyloxy, and moreespecially prop-2-enyloxy; alkynyloxy of three carbon atoms such asprop-1 and 2-ynyloxy, and the like, especially prop-2-ynyloxy; or Iphenoxy.

Preferably, R is trifluoromethyl; R is hydrogen; or C, or C alkyl,especially methyl; and R" is C, alkyl; di and tri chloro-methyl;trifluoromethyl; C alkenyl; pentachloro-C alkenyl; C, alkoxy,B-methoxyethoxy; C 3 alkenyloxy; C alkynyloxy; or phenoxy.

In particular, R is trifluoromethyl; R is hydrogen; and R" is C alkyl;dichloromethyl; or C, alkoxy.

The 2-amino-l ,3,4-thiadiazoles of formula (II) above required asstarting materials are, in part, known from the literature. Suchcompounds can be prepared, for example, by reaction of the appropriatel-acylthiosemicarbazides with agents which split off water, such asacetic anhydride [Chemische Berichte 29, 251] (1896)]. The new starting2-amino-l ,3,4- thiadiazole compounds can be prepared in the samemanner.

The carboxylic acid halides and anhydrides which may. be used asstarting materials according to the present invention are preciselydefined by formulae (III) and (IV) above. These carboxylic acid halidesand anhydrides are, of course, wellknown and readily available.

As examples of such starting acid halides of formula (III) which may bepreferably used, there are mentioned in particular: monochloroacetylchloride, dichloroacetyl chloride, 3-chloro-propionic acid chloride,perchloro-crotonic acid chloride, chloroformic acid methyl ester,chloroformic acid isopropyl ester, and the like.

As examples of such starting acid anhydrides of formula (IV) which maybe used, propionic anhydride and trifluoro-acetic anhydride areparticularly suitable.

In the following, further details for the two process variants [a] and[b] are given:

As inert solvent (which term includes a mere diluent), inert organicsolvents are particularly suitable. These include hydrocarbons, such asbenzene and toluene; ethers, such as diethyl ether, tetrahydrofuran anddioxan; esters, such as ethyl acetate; and nitriles, such asacetonitrile, and the like. In process variant [b], an excess of theanhydride may be expediently used as solvent.

In process variant [a], any of the customary acidbinding agents can beused. These include preferably alkali metal hydroxides, alkali metalcarbonates and tertiary amines. Especially suitable acid-binding agentsare sodium hydroxide, sodium carbonate, triethylamine,N,N-dimethylaniline, pyridine, and the like.

The reaction temperatures, in both process variants, can be variedwithin a fairly wide range. In general,=the reaction is carried out atsubstantially between about 20l ZObLC, preferably between about 20IOOC.

When carrying out the production process according to the presentinvention, in connection with the respective process variants,-about onemol of acid halide or one to two mols of acid anhydride may be used foreach mol of starting amino-thiadiazole. The working up of the reactionmixture may be effected in the customary manner.

Advantageously, the instant active compounds exhibit a strong herbicidalpotency and can therefore be used as weed killers. By weedsv are meantin the broadest sense all plants which grow in places where they are notdesired. Whether the active compounds according to the present inventionact as total or selective herbicidal agents depends on the amountapplied, as the artisan will appreciate.

The active compounds according to the present invention can be used, forexample, in the case of the following plants: dicotyledons, such asmustard (Sinapis), cress (Lepidium), cleaver (Galium), common chickweed(Stellaria), mayweed (Matricaria), smallflower Galinsoga (Galinsoga),fathen (Chenopodium), stinging nettle (Urtica), groundsel (Senecio),cotton (Gossypium), beets (Beta), carrots (Daucus), beans (Phaseolus),potatoes (Solanum), coffee (Coffea); monocotyledons, such as timothy(Phleum), bluegrass (Poa), fescue (Festuca), goosegrass (Eleusine),foxtail (Setaria), ryegrass (Lotlium), cheat (Bromus), barnyard grass(Echinochloa), maize (Zea), rice (Oryza), oats (Avena), barley(Hordeum), wheat (Triticum),

millet (Panicum), sugar cane (Saccharum); and the v Appropriately, theinstant active compounds also have only a slight toxicity towarm-blooded animals.

The instant active compounds also exhibit insecticidal, acaricidal andfungicidal properties, particularly against insects, acarids and fungiwhich infest plants.

The active compounds according to the instant invention can be utilized,if desired, in the form of the usual formulations or compositions withconventional inert (i.e. plant compatible or herbicidally inert)pesticidal diluents or extenders, i.e. diluents or extenders of the typeusable in conventional pesticidal formulations or compositions, e.g.conventional pesticidal dispersible carrier vehicles, such as solutions,emulsions, suspensions, emulsifiable concentrates, spray powders,pastes, soluble powders, dusting agents, granules, etc. These areprepared in known manner, for instance by extending the activecompoundswith conventional pesticidal dispersible liquid diluent carriers and/ordispersible solid carriers optionally with the use of carrier vehicleassistants, e.g. conventional pesticidal surface-active agents,including emulsifying agents and/or dispersing agents, whereby, forexample, in the case where water is used as diluent, organic solventsmay be added as auxiliary solvents. The following may be chieflyconsidered for use as conventional carrier vehicles for this purpose:inert dispersible liquid diluent carriers including inert organicsolvents, such as aromatic hydrocarbons (e.g. benzene, toluene, xylene,etc.), halogenated, especially chlorinated, aromatic hyrocarbons (e.g.chloro-benzenes), paraffins (e.g. petroleum fractions), chlorinatedaliphatic hydrocarbons (e.g. methylene chloride, etc.), alcohols (e.g.methanol, ethanol, propanol, butanol, etc.), ethers, ether-alcohols(e.g. glycol monomethyl ether, etc.), amines (e.g. ethanol-amine, etc.),amides (e.g. dimethyl formamide, etc.), sulfoxides (e.g. dimethylsulfoxide, etc.), ketones (e.g. acetone, etc.), and/or water; as well asinert dispersible finely divided solid carriers, such as ground naturalminerals (e.g. kaolins,

alumina, silica, chalk, i.e. calcium carbonate, talc,

kieselguhr, etc.), and ground synthetic minerals (e.g'. highly dispersedsilicic acid, silicates, e.g. alkali silicates, etc.); whereas thefollowing may be chiefly considered for use as conventional carriervehicle assistants, e.g. surface-active agents, for this purpose:emulsifying agents, such as non-ionic and/or anionic emulsifying agents)e.g. polyethylene oxide esters of fatty acids, polyethylene oxideethers of fatty alcohols, alkyl sulfonates, aryl sulfonates, etc., andespecially alkyl aryl-polyglycol ethers, magnesium stearate, sodiumoleate, etc.); and/or dispersing agents, such as lignin, sulfite wasteliquors, methyl cellulose, etc.

As will be appreciated by the artisan, the active compounds according tothe instant invention may be employed alone or in the form of mixtureswith one another and/or with such solid and/or liquid dispersiblecarrier vehicles and/or with other known compatible active agents,especially plant protection agents, such as other herbicides, orfungicides, insecticides, bactericides, etc., if desired, or in the formof particular dosage preparations for specific application madetherefrom, such as solutions, emulsions, suspensions, powders, pastes,and granules which are thus ready for use.

As concerns commercially marketed preparations,

about 0.005-0.5 preferably 0.008 to 0.1 percent, by

weight of the mixture. Thus, the present invention contemplates over-allcompositions which comprise mixtures of a conventional dispersiblecarrier vehicle such as (l) as dispersible inert finely divided carriersolid, and/or (2) a dispersible carrier liquid such as an inert organicsolvent and/or water preferably including a surface-active effectiveamount of a carrier vehicle assistant, e.g. a surface-active agent, suchas an emulsifying agent and/or a dispersing agent, and an amount ofv theactive compound which is effective for the purpose in question and whichis generally between about 0.005 to percent, and preferably 0.008 to 95percent, by weight of the mixture. 7

In particular, the amount of active compound applied per unit areavaries according tothe purpose intended, i.e. the effect desired, andthe mode of application. In general, substantially between about 0.25 20kg of active compound per hectare are applied, and preferably betweenabout 1-10 kgfof active compound per hectare, irrespective of thepresence or absence of the carrier vehicle.

In the usual aqueous preparations, and in the case of application afteremergence, the concentration of the active compound is, in general,substantially between about 0.005 to 0.5 percent, preferably.0.008 to0.1 percent, by weight of the mixture, as aforesaid.

The active compounds can also be used in. accordance with the well-knownultra-low-volume process with good success, i.e.-by applying such compound if normally a liquid, or by applying a liquid compositioncontaining the same, via very effective atomizing equipment in finelydivided form, e.g. av-erageparticle diameter of from 50-100 microns, oreven less, i.e. mist form, for example by airplane crop sprayingtechniques. Only up to at most about a few liters/hectare are needed,and often amount only up to about 1 quart/acre, preferably 2-16 fluidounces/acre, are sufficient. In this process it is possible to usehighly concentrated liquid compositions with said liquid carriervehicles containing from about 20 to about 95 percent by weight of theactive compound or even the percent active substance alone, e.g. about20 to 100 percent by weight of the active compound. 7

While the active'compounds can be used effectively according to thepre-emergence method, they are also particularly effective when usedaccording to the postemergence methodv Furthermore, the presentinvention contemplates methods of selectively killing, combatting orcontrolling undesired plants, e.g. weeds and the like, which comprise,applying to at least one of (a) such weeds and (b) their habitat, i.e.the locus to be protected, a

herbicidally effective or toxic amount of the particular compound of theinvention alone or together with a carrier vehicle as noted above. Theinstant formula tions or compositions are applied in the usual manner,for example by spraying, atomizing, scattering, dusting, watering,sprinkling, and the like, whether for preemergence application to thesoil or post-emergence application to the weeds.

It will be realized, of course, that in connection with thepre-emergence use of the instant compounds as well as the post-emergenceuse thereof, the concentration of the particular active compoundutilized in admixture with the carrier vehicle will depend upon theintended application and may be varied within a fairly wide rangedepending upon the weather conditions, the purpose for which the activecompound is used, e.g. for

total or only selective herbicidal effect, and the plants given activecompound. It is expedient to keep constant the amount of water per unitarea. The concentration of the active compound in the given preparationis of no importance, only the amount of active compound applied per unitarea being decisive. After three weeks, the degree of damage to the testplants is determined and characterized by the values -5, which have thefollowing meaning:

0 no effect 1 slight damage or delay in growth 2 marked damage orinhibition of growth 3 heavy damage and only deficient development oronly 50 percent emerged 4 plants partially destroyed after germinationor only 25 percent emerged 5 plants completely dead or not emerged. Theparticular active compounds tested, the amounts applied and the resultsobtained can be seen from the following Tables 1a and lb:

TABLE larvae-amelioration TEST Amount of active compound applied in kg,/Cheno- Active compound hectare podium Sinapls Cotton Oats Wheat (13)., 0cm 20 4 5 2 5 5 H 1n 4 5 1- 4-5 5 NIICO-C1I 5 3 4 1 4 4-5 (Known) 20 5 55 3 z (31) 5 5 4-5 1 i i 5 5 5 4-5 0 0 TABLE 1b.-PltE-El\1ERGENCE TESTAmount of active compound applied in kg,/ Echino- Clieno- Activecompound hectare ehloa podium Sinapis Cotton Wheat (A) .l o 2 1 4 0 1 H10 1 o 2 0 u 01- NllC-(,llrCll5 5 0 0 0 u 0 (Known.)

I 20 5 5 5 5 5 (4,) in 5 5 5 5 4-5 i 5 4-5 5 5 4 '-l 20 H5 5 3 2-3 (15).'10 :i 5 .5 l l i 5 2 r 5 u 11 tion, the herbicidal activity of theparticular active EXAMPLE2 compounds of the present invention.

Post-emergence test EXAMPLE 1 Solvent: 5 parts by weight acetonePie-emergence test Emulsifier: 1 part by weight alkylaryl polyglycolSolvent: 5 parts by weight acetone ether Emulsifierl I P y Weightalkylaryl P y y To produce a suitable preparation of the particularether active compound, 1 part by weight of such active com To produce asuitable preparation of the particular pound is mixed with the statedamount of solvent, the stated amount of emulsifier is added thereto, andthe resulting concentrate is then diluted with water to the desiredfinal concentration.

Test plants which have a height of about 5 to 15 cm. are sprayed withthe preparation of the given active compound until just dew moist. Afterthree weeks, the degree of damage to the plants is determined andcharacterized by the values -5, which have the fol- E21; 2 g:$( n)= (C)-CCla lowing meaning: k CHZCHH 73 0 no effect 3, 8%,: Sgt, CH 136 H(145 1 a few slightly burnt spots (16) H OCH 2 162 2 marked damage toleaves I (11!) cps H OCHZCH=CH2 57 3 some leaves and parts of stalkspartially dead 53 5 8g C CH :33 4 plant partially destroyed (14:) CH3 1127/11 mm Hg 5 plant completely dead. (15,) CF CH OC,,H 1 9 Theparticular active compounds tested, their con- (161) F8 H (ZHPCHPCWCHBE119 (l7 CF: H L=CH2 101 centrations, and the results obtained can beseen from the following Table 2: H1

TABLE 2.POSTJ\7ITEWENOE TEST Concentration of active compound l lo-hintChono- Active com pound in percent cliloa podium Sinapis Unts Wheat (0 vA. on; 0.1 a a 4 a 3 0.05 2 2. a z 1 N1IC()- Cll 0. 025 z a 2 1 1 (Known(A) r. o 1 5 a 5 a a 11 0.05 5 a 5 a z (:1- -N1r-o-cn2-mn 0.025 s 5 5 1l or (KnowuJ 0. 4-5 s s A 4 (3,) .q. 0. 05 4 5 5 1 i 0. 025 3 5 5 0 00.1 4 n 5 a 4 (4,).....-. .l 0.05 2 rs n z 2 r 0.020 0 4 5 1 2 0.1 M n 5i 4 (11) 0. 05 4 4-5 a t a 0. 025 2 a 5 1 3 0.1 5 5 5 4 a (21) 0. 05 4-5a a a a v 0.025 a 5 44a 0 2 The following further examples are set forthto illus- (18,) CF H OCH CH OC'H 14B trate, without limitation, theprocesses for producing 40 the active compounds according to the presentinven- These compounds may be designated: tion. 4. 2acetylamino-5-trifluoromethyl-l ,3,4-thiadiazole I i 5.2-trichloroacetylamino-5-trifluoromethyl-1 ,3,4- EXAMPLE 3 (variant (a1)thiadiazole v 6. 2-(1,2',3',3',3'-pentachloro -prop-1-enylcarbon- Tylamino-S-trifluoroemthyl-l ,3 ,4-thiadiazole 7.2-(N-methyl-N-dichloroacetyl-amino)-5- CF L J or1 c a a H (10trrfluoromethyl-l ,3,4-thiadlazole 8. 2-(N-methyl-N-propionyl-amino)5-10.1 g. (0.1 mol) triethylamine are added to 16.9 gtrifluoromethyl-l,3,4-thiadiazole I (0.1 mol) 2-amino 5-trifluoromethyll,3,4-thiadiazole 3. 2-methoxycarbonylarnmo-S-tr|fluoromethyl- I in 100ml tetrahydrofuran, and 14.7 g (0.1 mol) l.3i4jthiadiazoledichloroacetyl chloride are slowly added dropwise at P QP Y y a P y 20C.Stirring is continued for one hour. Suction filtra- PA- f y y tion fromthe precipitated triethyl-amine hydrochloridetrlfluoromethyl'l13|44llladlaml is thence effected, and thereafter thefiltrate is concenl 'P 'P' fenylnxycarbonylammo's" trated by evaporationand the residue is recrystallizedtl'lfluol'omethyl'l,314'tl11adlamlefrom benzene. The2-dichloroacetylamino-5 jmloxycarbonylammodtrifluoromethyhl,3,4-thiadiazole thereby obtained mfluommethyl'li3r4'thladliizole m'eltsat 176C. 6Q 13. 1 2-phenoxycarbonylamrnod-trlfluoromethylln analogousmanner, the thiadiazoles of formula (I) l3t4'thladlazole 1 y abovementioned in Table 3 also prepared: r x w 1- trifluoromethyl-l,3,4-thiadiazole TABLE 3 l5. 2-( N-methyl-N-phenoxycarbonyl-amino)-5- RR, R C b a trifluoromethyl-l,3,4-thiadiaz0le (45) CF H CH3 C 16. 2-(4-methyl-butylcarbonyl-amino(-5- (5,) (F3 H CC| trifluoromethyl-l,3,4-thiadiazole 17. 2-(1-methyl-vinylcarbonyl-amino(-5- Ytrifluoromethyl-l,3,4-thiadiazole l8. 2-(2-methoxy-ethoxycarbonylamin0-5trifluoromethyl-l ,3,4-thiadiazole EXAMPLE 4 (variant [b]) abovementioned in Table 4 is also prepared:

TABLE 4 R R' R" m.p. "C b.p. C (2 CF; H CHfCH; l77

This compound may be designated: 2.2-propionylamino-5-trifluoromethyl-1,3,4-

thiadiazole It will be realized by the artisan that all of the foregoingcompounds contemplated by the present invention possess the desiredselective or total herbicidal properties, and especially the capabilityof selectively destroying weeds, as well as a comparatively low toxicitytoward warm-blooded creatures and a concomitantly low phytotoxicity Ywith respect to higher plants, enabling such compounds to be used withcorrespondingly favorable compatibility with respect to warm-bloodedcreatures and higher plants for more effective control and/orelimination of weeds by selective application of such compounds to suchweeds and/or their habitat. Nevertheless, the instant compounds possesstotal herbicidal action when used in large quantities, althoughselective herbicidal action is obtained when used in smaller quantities.As contemplated herein, the term weeds is meant to include not onlyweeds in the narrow sense, but also in the broad sense, whereby to coverall plants and vegetation considered undesirable for the particularpurposes in question.

It Wlll be appreclated that the instant specification and examples areset forth by way of illustration and not limitation, and that variousmodifications and changes may be made without departing from the spiritand scope of the present invention.

What is claimed is:

l. 2-( l ,2,3,3,3-Pentachloro-prop-l '-enylcarbonylamino)5-trifluoromethyl-l,3,4-thiadiazole of the formula

